Carbon Films Research Articles

Crystallization and Silicon Carbide Formation in Two-Layer Amorphous Silicon–Carbon Films during Electron Irradiation

Crystallization and Silicon Carbide Formation in Two-Layer Amorphous Silicon–Carbon Films during Electron Irradiation

Nanostructured Carbon Films Obtained by CH4 Plasma Deposition and Annealing at High Temperatures: Structural Features and Their Influence on the Electrical and Optoelectronic Properties

Nanostructured Carbon Films Obtained by CH4 Plasma Deposition and Annealing at High Temperatures: Structural Features and Their Influence on the Electrical and Optoelectronic Properties

Properties of Carbon Films on Glass Depending on the Conditions of Implantation with Argon Ions

Properties of Carbon Films on Glass Depending on the Conditions of Implantation with Argon Ions

In-situ zinc vanadate layer derived from highly hydrophilic substrate for PEC performance enhancement of Zn-doped BiVO4 photoanode

Owing to serious concerns regarding environmental issues, extensive research is being conducted to develop eco-friendly and sustainable energy sources. One promising solution is the utilization of solar energy for energy production using photoelectrochemical (PEC) methods. However, the performance of photoanodes is frequently hindered by high recombination rates and inadequate charge transport. To address these issues, we designed an approach that incorporates an ultrathin hydrophilic carbon (UTHC) film on a substrate. The UTHC film enhanced the hydrophilicity of the FTO surface and enabled the synthesis of a zinc vanadate layer for efficient charge transfer. As a conductive bridge, the zinc vanadate layer promotes effective charge transfer for excellent PEC performance. The resulting carbon film/Zn-doped BiVO4 (CZB) photoanode exhibited significantly improved PEC performance, achieving a remarkable photocurrent density of 1.515 mA∙cm−2 and a separation efficiency of 9.58 % at 1.23 VRHE. This study demonstrates a potential method for enhancing PEC performance for sustainable energy conversion using a highly hydrophilic metal oxide layer on an FTO substrate.

Vacuum tribological properties in Cr-doped H-DLC self-lubricating radial spherical plain bearings

To improve the vacuum tribological properties of the self-lubricating radial spherical plain bearings (SSPBs), the multi-layered Cr-doped hydrogenated diamond-like carbon films (Cr-H-DLC) and non-doped H-DLC films as the lubricating materials were prepared on the inner ring with an outer spherical surface and the outer ring with an inner spherical surface by unbalanced magnetron sputtering. The microstructure, phase composition, tribological properties, and failure mechanism of Cr-H-DLC SSPBs and H-DLC SSPBs were investigated. The results showed that the microstructure of the outer and inner spherical surfaces for the two kinds of SSPBs was dense. The microgram indicated that the self-lubricating film thickness of the outer spherical surface was greater than that of the inner spherical surface. What is more, the Raman spectra showed that the self-lubricating coating on the outer spherical surface contains more graphite characteristics of sp2 hybrid bonds based on the value of ID/IG. According to the vacuum tribological test, the oscillating life of H-DLC SSPBs was higher than that of Cr-H-DLC SSPBs. Moreover, the change law of friction torque and friction temperature rise showed that the testing process of coated SSPBs could be divided into running-in, stable, and failure periods. Compared with the ID/IG values before and after the vacuum test, it could be inferred that the graphitization of the sp3 hybrid bond in the self-lubricating film on both spherical occurred. Based on the microscopic wear morphology, the failure mechanism of H-DLC SSPBs and Cr-H-DLC SSPBs were abrasive wear and fatigue wear. When the lubricating layer of the friction interface was worn, the metal substrate of the inner and outer rings would contact, resulting in adhesive wear.

Smooth diamond-like carbon films prepared by cathodic vacuum arc deposition with large glancing angles

Diamond-like carbon (DLC) films were prepared by cathodic vacuum arc (CVA) deposition with different glancing angles (the angle between the normal reverse direction of the arc target and the normal direction of the substrate surface) in range of 0 to 135°. The effects of the glancing angle on the morphology, carbon structure, mechanical property and tribological behavior of the DLC films were investigated. The results show that the surface quality of the DLC films is significantly improved by increasing the glancing angle. The macroparticles in the surface as well as the surface roughness of the DLC films decrease sharply as the glancing angle increases. The sp3/sp2 of the DLC films decreases at first and then increases as the glancing angle increases. The normal incidence energy of the Cn+ species becomes suitable to the formation of sp3-C when the glancing angle is 45°. The variation in the film hardness and compress stress at different glancing angles are similar in profile to the sp3 bond fractions. However, the compressive stress of the films could be reduced effectively by avoiding the bombardment of the Cn+ species with excessively high energy through increasing glancing angle. The tribological behaviors of the films could be also improved by changing the glancing angle. It is supposed that the CVA with appropriate glancing angle might be one way to prepare the DLC films with smooth surface, high hardness, low compressive stress and good tribological performance.

Creattion of silicon-carbon films by induction assisted plasma chemical deposition

Silicon-carbon films are of great interest as diamond-like materials combining unique properties – high hardness, adhesion to a wide class of materials, abrasion resistance, as well as chemical resistance, low coefficient of friction and biocompatibility. The presence of silicon in the composition makes it possible to significantly reduce the internal mechanical stresses in such coatings compared to diamond ones. In modern production, films have been used primarily as solid lubricants and protective coatings. There are a large number of methods for producing silicon-carbon films, the most widespread among which are various variants of vapor-phase chemical deposition. In this paper, a method for the synthesis of silicon-carbon films was proposed and tested, based on the use of a high-frequency inductor to produce a plasma of vapors of silicon-carbon liquid injected into the chamber from an external source. Pure silicon-carbon films with a carbon atom content with sp3-hybridized orbitals of 63–65 % were obtained on sitall substrates. The composition, surface roughness and coefficient of friction of unalloyed silicon-carbon films obtained by the proposed method were studied. The possibility of resistive switching in thin silicon carbon films in crossbar structures with metal electrodes was studied.

The occurrence of ultralow friction even superlubricity for graphene oxide/hydrogenated diamond-like carbon composites in multi-environments

The establishment of ultralow friction and superlubricity can significantly decrease the dissipation of energy and failure of parts in moving mechanical systems. Hydrogenated diamond-like carbon (H-DLC) film can realize the frictionless state at engineering scale by the stress-induced graphitization that leads to the formation of the vital superlubricious structures: graphene-like carbon and onion-like carbon during the sliding process. Herein, we designed some composites by combination H-DLC film and graphene oxide (GO) nanosheets to provide the “pre-graphitized” sliding interface for decreasing the friction. Frictional behaviors of these composites in different atmospheres and the as-formed structures of sliding interfaces were investigated comprehensively in this work. It was demonstrated that the existence of GO on H-DLC film could significantly decrease the friction and even establish the near friction-vanishing state. The structural investigations showed that the existence of GO on H-DLC film could work as a “pre-graphitization” process, hinder the structural evolution of H-DLC film from amorphous to sp2-rich ones and endow the composite with ultralow friction even superlubricious performance. The investigation would provide some helpful advices for H-DLC film to establish ultralow even superlow friction from inert atmospheres to humid air at engineering scale by depositing GO flakes on the surface of H-DLC film.

Accelerating Macroscale Superlubricity through Carbon Quantum Dots on Engineering Steel Surfaces

AbstractMacroscale superlubricity on engineering steel surfaces offers a promising solution for minimizing friction and wear in engineering applications. However, achieving superlubricity typically requires a long running‐in period, which may result in significant wear for the friction pair. Herein, a new lubricant with superlubricating properties is rationally designed by using polyethylene glycol (PEG) and critic acid (CA) under complexing effect with a running‐in period of about 800 s. Importantly, the introduction of carbon quantum dots (CQDs) obtained from the pyrolysis of CA into PEG aqueous solution shortens the running‐in period for achieving macroscale superlubricity (µ ≈ 0.005) between steel/steel contact to 44 s. The corresponding wear rate (1.15 × 10−7 mm3 N−1 m−1) on the steel disk is reduced by 77% due to the shorter running‐in time. Furthermore, the surface analysis combined with the molecular dynamics simulations demonstrates that CQDs easily adsorb on the surface of the friction pair, forming a carbon film that reduces interaction energy between the lubricant molecules and the substrate. This work provides new insights into the lubrication mechanism of CQDs and contributes to the design of liquid superlubricants with short running‐in periods and low wear rates on engineering steel surfaces.

Temperature-structure-induced metastable structural transformation mechanism of the amorphous carbon film during friction

Temperature has a significant impact on the tribological behavior of amorphous carbon films. However, the fundamental question of "the effect of temperature-structure-induced on metastable structural transformation mechanism of amorphous carbon films " is not well understood. This study is conducted to get an insight into the temperature-structure-induced structural transformation of amorphous carbon films. The relevant studies show that the effect of high temperature within a certain threshold on the "sp3-C to sp2-C" and the structural ordering degree changes from inhibition to promotion with amorphous carbon films’ density increases, and the structural transformation of high-density amorphous carbon films responds more significantly to temperature changes. The structural ordering degree of amorphous carbon films is promoted when the temperature exceeds a certain threshold.

Influence of process parameters including the confining magnetic field of a plasma beam source on the deposition of N‐doped hydrogenated carbon films

Electrically conductive nitrogen‐doped hydrogenated carbon films (a‐C:H:N) were deposited using a nitrogenacetylene gas mixture by plasma‐assisted chemical vapor deposition (PACVD). A capacitively coupled plasma beam source was used for the depositions. The plasma is excited by a radio‐frequency (RF) discharge and confined by Helmholtz magnetic coils, resulting in an increase in plasma density. The ion energy, as well as the deposition rate, can be controlled by the choice of the size of the coupling electrode, i.e. the ratio of cathode-to‐anode area, the electric current at the Helmholtz magnet coils, the total gas pressure and the RF power. The interdependence of these process parameters on the ion energy and the deposition rate has been studied in detail in this work. Hardness and electrical resistivity were measured on the deposited a‐C:H:N films.

Enhancing tribological performance of graphene sheet-embedded carbon films on steel substrates via texture engineering and chromium doping

Amorphous carbon (a-C) film is a promising solid lubricant coating due to its unique structure and excellent properties. However, its poor adhesion and long running-in period hinder the application in metal components. Graphene sheet-embedded carbon (GSEC) film has a significantly shorter running-in period but suffers from inferior tribological properties due to its rough surface and weak mechanical characteristics. In this study, we utilized an electron cyclotron resonance (ECR) plasma nano-surface manufacturing device to deposit GSEC films onto steel substrate surfaces. By manipulating the surface/interface texture and incorporating chromium (Cr) doping, the tribological properties of the GSEC films were improved both chemically and physically. The results demonstrated that the textured carbon film exhibited superior adhesion to the steel substrate and a wear life that was three orders of magnitude longer than the untextured GSEC film, under low normal load conditions while sliding against the GCr15-bearing steel ball. After doping the Cr into textured carbon films, there was a significant reduction in the friction coefficients, and the wear type of carbon film transformed from adhesive wear to abrasive wear. Moreover, the doped carbon films demonstrated prolonged wear lives under high normal loads. This improvement can be attributed to the formation of hard CrC nanocrystalline, which effectively reduced surface roughness and enhanced the mechanical properties of the carbon films. Notably, even under a contact pressure of 0.83 GPa, the doped carbon film maintained favorable tribological performances. These findings have extended the potential applications of carbon films on metal substrates.

Formation of Trachytes from Wangtian’e Volcanic Neck of the Changbaishan Area (Northeast China) as a Result of Tholeiitic Magma Crystal Fractionation

Tholeiitic basalts and trachytes of the bimodal association of Wangtian’e volcano are studied. It is shown that trachytes formed with the leading role of crystal fractionation of the parental tholeiitic magma. It has been identified from the melt inclusion study that hedenbergite and plagioclase phenocrysts of trachytes from Wangtian'e volcanic neck crystallized in the temperature range of 1080–1100 and 1050–1060°C, respectively. After heating experiments with melt inclusions in plagioclase of trachytes, in some cases relics of carbonates and CO2 were observed in the inclusions. The trachyte phenocrysts host water-bearing Fe-rich globules and CO2 inclusions with carbonate phases. The Fe-rich silicate globules are often intergrown with titanomagnetite and are covered by amorphous carbon films. A model is suggested explaining the formation of water-bearing Fe-rich globules and CO2 inclusions with carbonate relics as a result of silicate–silicate and silicate–carbonate liquid immiscibility, that was caused by the evolution of the parental basaltic melt. Upon the trachytic melt ascending to the surface, the ferrocarbonate liquid was decomposed on magnetite, carbon, and carbon dioxide.

Low friction and wear of Nitrogen-doped diamond-like carbon films deposited on NBR with different flows of N2 by DC-MS

Utilizing a diamond-like carbon (DLC) coating on rubber surfaces is an innovative approach to improve the wear resistance and tribological characteristics of rubber. In this paper, a series of N-doped diamond-like thin films (N-DLC) were deposited on the surface of nitrile butadiene rubber (NBR) substrate by varying the flow rate of nitrogen using direct current magnetron sputtering (DC-MS) technology, and the effects of nitrogen flow rate on the surface morphology, structure, surface energy and tribological properties of N-DLC films were systematically investigated. The results show that the friction coefficients of the N-DLC films are all smaller than those of the undoped DLC films, and most importantly, the samples maintain a stable, ultra-low coefficient of friction of about 0.057 and a low wear rate of the order of 10−9 in the tribological tests at a nitrogen flow rate of 3 sccm, exhibiting excellent tribological performance. This is attributed to several key factors: higher hardness, better film-base bonding, lower surface roughness, and lower friction interface adhesion. This recognition provides insight into the preparation of N-DLC films on rubber to achieve low frictional wear.

Surface sulfurization of amorphous carbon films in the chemistry of oxygen plasma added with SO2 or OCS for high-aspect-ratio etching

Etching of oxygen-based plasmas with sulfur dioxide (SO2) or carbonyl sulfide (OCS) can form high-aspect-ratio (HAR) features of amorphous carbon films as carbon hard masks (CHM). The etched profiles showing shapes such as bowing or tapering are essentially dependent on the partial pressures of SO2 or OCS in the O2 plasma. The surface treated after the OCS-added plasma exhibited strong sulfurization by S2 and CS species in S 2p of the X-ray photoelectron spectroscopy (XPS). The gas-phase interactions in the sulfur-oxygen-carbon system generated atoms and molecules, such as O, O+, and O2+, which etched at the bottom and, conversely, SO, CO, CS, CS2, and S2, which inhibited isotropic etching at the sidewalls of the HAR features. The chemical reactions of the CS sulfurizing precursors in the gas phase were monitored by comparing their optical emission intensities at a wavelength of 257 nm with those of SO2 at approximately 320 nm. The optimization of the HAR profiles of the CHM can be controlled by sidewall sulfurization of the CHM to obtain desirable profile shapes for the HAR features.

Microstructure and high-temperature tribological properties of Ti/Si co-doped diamond-like carbon films fabricated by twin-targets reactive HiPIMS

In order to enhance high-temperature tribological properties of the diamond-like carbon (DLC) films, Ti/Si co-doped DLC films were synthesized by twin-targets reactive high power impulse magnetron sputtering and effects of doped elements on mechanical performances were investigated. The results showed that a mid-doped DLC film with a Ti content of 13.8 at.% and a Si content of 12.6 at.% obtained the best high temperature tribological performance and its wear resistance was significantly less affected. The friction coefficient of the Ti/Si co-doped DLC film at 450 °C dropped to as low as 0.08. In addition, compared with the mono Ti-doped DLC film, its wear rate at 450 °C decreased from 5.24 × 10−4 to 1.40 × 10−5 mm3·N−1·m−1. Raman spectra revealed that Si could hinder the sp3-C to sp2-C transition at elevated temperatures, which impeded adhesive wear in the high temperature tribological process.

Investigation of Adsorption Kinetics on the Surface of a Copper-Containing Silicon–Carbon Gas Sensor: Gas Identification

The low selectivity of materials to gases of a similar nature may limit their use as sensors. Knowledge of the adsorption kinetic characteristics of each gas on the surface of the material may enable the ability to identify them. In this work, copper-containing silicon–carbon films were formed using electrochemical deposition on the Al2O3 substrate with interdigitated Cr/Cu/Cr electrodes. These films showed good adsorption characteristics with several different gases. The adsorption kinetics of nitrogen dioxide, sulfur dioxide, and carbon monoxide on the film surface were investigated by the change in the resistivity of the material. Pseudo-first-order and pseudo-second-order kinetics, Elovich, Ritchie, and Webber intraparticle diffusion models were applied. It was found that the largest approximation factor and the lowest Root-Mean-Square Error and Mean Bias Error for all three gases were for the Elovich model. The advantages of silicon–carbon copper-containing films for gas sensor applications were shown. An algorithm for gas recognition was proposed based on the dependence of the change in the resistivity of the material under stepwise gas exposure. It was found that parameters such as the values of the extrema of the first and second derivatives of the R vs. t dependence during adsorption and the slope of R vs. t dependence in the Elovich coordinates are responsible for gas identification among several one-nature gases.

Atomistic Insights into Interfacial Optimization Mechanism for Achieving Ultralow-Friction Amorphous Carbon Films under Solid-Liquid Composite Conditions.

The combination of fluid lubricants and textured amorphous carbon (a-C) can provide an ultralow friction state, which can improve the reliability and service life of dynamic machinery. However, the coupling effects of the contact pressure and oil content on the friction-reducing efficiency is still lack of study, and the corresponding friction mechanism is also not fully understood, which cannot be achieved by experiment due to the limitation of in situ characterization. In this study, using the reactive molecular dynamics simulation, the insight into the evolution of interfacial structures induced by both contact pressures and oil contents on a-C surface was systematically investigated to explore the fundamental mechanism. In particular, the friction difference between textured and untextured a-C films was evaluated comparatively. Results indicate that the tribological performance strongly depends on the interfacial lubrication state, which is jointly determined by the oil content and contact pressure; the best operating condition to achieve ultralow friction coefficient (0.002) is obtained, and the evolution of friction coefficient with oil content and contact pressure is highly dominated by the lubricant mobility, cross-linking between mating a-C surfaces, or competition/synergy of the H stress state from the lubricant with interfacial passivation. Furthermore, the difference in friction reduction between textured and untextured systems is unveiled; with the increase of contact pressure, the role of texturing a-C surface in antifriction changes from positive to negative effect, which is related to the transformation of interfacial hybridized structure and anomalous flow of lubricant. These results can significantly enhance the understanding of composite lubrication systems through computation and also provide a roadmap for the R&D of the advanced lubrication system according to the working conditions.

Facile fabrication of conductive graphitic carbon films as transparent electrodes in organic solar cells by ion beam irradiation of polystyrene films and carbonization

Conductive graphitic carbon films were fabricated from insulating polystyrene (PS) by ion beam irradiation and subsequent thermal treatment, and used as a transparent anode for organic solar cells (OSCs). Analyses of optical and chemical properties revealed that the thermally resistant oxidized carbon clusters in the PS precursors (spin-coated on quartz) were efficiently generated by ion beam irradiation at a fluence of 2 x 1016 ions/cm2, and transformed to graphitic carbon thin films through high-temperature treatment. The graphitic carbon films exhibited thickness-dependent conductivity (the highest conductivity of 374 S/cm), while their work function (5.20 eV) and surface roughness (0.560–0.596 nm) were unaffected by the thickness of the films. Furthermore, the introduction of the 10.2 nm-thick graphitic carbon films into poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61 butyric acid methyl ester (PCBM)-based OSCs resulted in a power conversion efficiency (PCE) of 1.40%, demonstrating the feasibility of using the graphitic carbon films as transparent electrodes.

Nanoscale friction of tetrahedral amorphous diamond-like carbon film after thermal annealing

Diamond-like carbon (DLC) coatings have demonstrated significant potential as solid lubricants for a wide range of applications. However, thermal-induced structural changes lead to alterations in its mechanical and frictional properties. In this study, we investigate the friction properties of DLC films after high-temperature annealing, by conducting reciprocating single asperity scanning experiments of self-mated hydrogen-free DLC tribopair under ultra-high vacuum (UHV) conditions. As the annealing temperature increases, the coefficients of friction (COFs) first increase owing to the desorption of water molecules; while, with the further increase of temperature, friction shows a decreasing trend because of the high-temperature-induced sp3-to-sp2 rehybridization which lowers the interfacial shear strength. The insights gained from this study provide a better understanding of the frictional properties of DLC films.